Deep fiber network with high speed data and video on demand

ABSTRACT

Optical interface units are provided for transmitting data and video signals in a deep fiber network. The optical interface units may include a first type which is situated in a central location, such as at a host digital terminal in a central office location, and a second type which is situated near a subscriber location, such as at an optical network unit. The first type of optical interface unit combines downstream video signals at a first wavelength with downstream data signals at a second wavelength and also receives upstream data signals at the second wavelength. The second type of optical interface unit receives the transmissions from the first type of optical interface unit at the first wavelength and transmits the upstream data signals at the second wavelength. Various embodiments of the optical interface units are provided for extending the functionality of the network to provide high speed data and video on demand services.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority from and is related to U.S.Provisional Application No. 60/306,906 entitled “DFHFC With High SpeedData and VOD,” which was filed on Jul. 20, 2001. The entire disclosureof U.S. Provisional Application No. 60/306,906 is hereby incorporatedinto the present application by reference.

BACKGROUND OF THE INVENTION

[0002] 1. Technical Field

[0003] The present invention generally relates to methods and apparatusfor carrying on communications over optical fibers. More specifically,the invention is directed to methods and apparatus to providebi-directional telephonic communication and bi-directional digital datatransmission such as digital subscriber line services and transmittingmulticast TV.

[0004] 2. Description of the Related Art

[0005] The communications industry is using more and more optical fibersin lieu of copper wire. Optical fibers have an extremely high bandwidththereby allowing the transmission of significantly more information thancan be carried by a copper wire transmission line such as twisted pairsor coaxial cable.

[0006] Of course, modern telephone systems require bi-directionalcommunications where each station or user on a communication channel canboth transmit and receive. This is true, of course, whether usingelectrical wiring or optical fibers as the transmission medium. Earlytelephone communication systems solved this need by simply providingseparate copper wires for carrying the communications in each direction,and this approach is still used in older installations where telephonyis the only required service. It is also often used even where digitaltransmission service is demanded as the signals get closer to the endusers. Although twisted pairs and coaxial cables are used in homes anddistribution terminals close to the home end user, some moderntelecommunication systems now use microwave and optic fibers astransmission mediums.

[0007] Because of extremely high bandwidths available for use by anoptical fiber, a single fiber is quite capable of carrying a greatnumber of communications in both directions. One technique of opticaltransmission is WDM (wavelength divisional multiplexing) and usesdifferent wavelengths for each direction of travel.

[0008] Another area of rapidly growing technology is providingunidirectional TV signals by cable to a multiplicity of subscribers orusers (multicast). In the past, such signals were and still aretypically transmitted by the use of coaxial cables (e.g. cable TV).However, the use of optical fibers for transmission allows broad bandtransmission to a large numbers of customers and, since substantiallyall of the transmission of TV signals is one way (i.e. unidirectional),if a single optical fiber were used solely for the TV signals therewould be almost no use of the selected wavelength of light for carryingreturn signal, which are typically control or information signals.

SUMMARY OF THE INVENTION

[0009] A communication system for providing high speed data services toa subscriber using optical fibers is provided. The communication systemcomprises, a first optical interface unit (OIU) in a network nodeelement and a second OIU in a optical node device. The first OIUcomprises a first electrical-to-optical (E/O) circuit, a firstoptical-to-electrical (O/E) circuit, a first diplexer device, and afirst modem. The first E/O circuit is operative to receive firstelectrical signals, convert the first electrical signals to firstoptical signals of a first wavelength, and transmit downstream on anoptical fiber the first optical signals. The first O/E circuit isoperative to receive second optical signals from the optical fiber,convert the second optical signals to second electrical signals, and totransmit the second electrical signals upstream. The first diplexerdevice is coupled between the optical fiber and the first E/O circuitand is also coupled between the optical fiber and the first O/E circuit.The first modem is coupled between the first O/E circuit and a highspeed data source and is coupled between the first E/O circuit and thehigh speed data source for providing a high speed data path in the OIU.

[0010] The second OIU comprises a second E/O circuit, a second O/Ecircuit, a third O/E circuit, a first triplexer device, and a secondmodem. The second E/O circuit is operative to receive third electricalsignals, convert the third electrical signals to the second opticalsignals of a second wavelength, and transmit upstream on the opticalfiber the second optical signals. The second O/E circuit is operative toreceive third optical signals of a third wavelength from the opticalfiber, convert the third optical signals to fourth electrical signals,and to transmit the fourth electrical signals downstream to asubscriber. The third O/E circuit is operative to receive the firstoptical signals from the optical fiber, convert the first opticalsignals to fifth electrical signals, and to transmit the fifthelectrical signals downstream to a subscriber. The first triplexerdevice is coupled between the optical fiber and the second E/O circuit,is coupled between the optical fiber and the second O/E circuit, and iscoupled between the optical fiber and the third O/E circuit. The secondmodem is coupled between the third O/E circuit and a high speed datasubscriber and between the second E/O circuit and the high speed datasubscriber for providing a high speed data path in the second OIU.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] In order that the invention identified in the claims may be moreclearly understood, preferred embodiments of structures, systems andmethods having elements corresponding to elements of the inventionrecited in the claims will be described in detail by way of example,with reference to the accompanying drawings, in which:

[0012]FIG. 1 is a block diagram of an exemplary HFC system;

[0013]FIG. 2 is a more detailed diagram of a HFC system that shows anexemplary head end and exemplary HDT;

[0014]FIG. 3A is a schematic diagram illustrating a first embodiment ofan OIU in a HDT;

[0015]FIG. 3B is a schematic diagram illustrating a first embodiment ofan OIU in an ONU;

[0016]FIG. 3C is a schematic diagram illustrating an exemplary signalspectrum for signals transmitted and received by the OIUs in the HDT andONU;

[0017]FIG. 4 is a more detailed schematic diagram illustrating a firstembodiment of an OIU in a HDT;

[0018]FIG. 5 is a more detailed schematic diagram illustrating a firstembodiment of an OIU in a ONU;

[0019]FIG. 6 is a schematic diagram illustrating a first alternativeembodiment of an OIU in a HDT;

[0020]FIG. 7 is a schematic diagram illustrating a first alternativeembodiment of an OIU in an ONU;

[0021]FIG. 8 is a schematic diagram illustrating a second alternativeembodiment of an OIU in a HDT;

[0022]FIG. 9 is a schematic diagram illustrating a second alternativeembodiment of an OIU in an ONU; and

[0023]FIG. 10 is a schematic diagram illustrating a third alternativeembodiment of an OIU in an ONU.

DETAILED DESCRIPTION

[0024] Shown in FIG. 1 is a preferred embodiment of a fiber-to-the-curb(FTTC) communication system 10 for delivering residential and/orbusiness telecommunication services over a hybrid fiber-coaxial (HFC)distribution network 12. This embodiment takes partial advantage of theexisting telephone and coaxial TV distribution systems 26 while alsousing a single optical fiber 24 for part of the bi-directional telephonetransmission (POTS) as well as part of the transmission path between avideo source location 14 and a building or home 32. The exemplarycommunication system 10 comprises a cable head-end 14, one or morenetwork nodes such as host digital terminals or points-of-presence 16,optical fibers 18, 20 that provide communication paths between the hostdigital terminal and the cable head-end, a plurality of optical nodedevices 22, optical fibers 24 that provide communication paths betweenthe optical node devices 22 and the host digital terminal 16, andcoaxial distribution plants 26 that comprise coaxial and other coppercables 28 and splitters/amplifiers 30 that are used to distributesignals to homes and/or businesses 32 that subscribe to servicesprovided by the communication system 10. It should be noted that,although the following discussion is in terms of a single direct pathfor the coaxial and optical fiber cable between two locations 14 and 32,in actuality there will be a significant amount of multiplexing andde-multiplexing such that many subscribers or customers may be servicedby the single optical fiber and other multiplexed cables. It should alsobe noted that there might also be several amplification stations locatedat various locations in the distribution path. Further, as is shown, inaddition to the optical fibers 18 and 20 traveling between the head end14 and the HDT 16, there will be other optical fibers as indicated byoptical fibers 18A and 20A that extend between the head end 14 and otherHDTs 16A.

[0025] The cable head-end 14 provides the communication system 10 withvideo programming, such as television (TV) programming or video ondemand, that is to be passed on to subscribers and may also providecable modem services to subscribers. In distributing cable televisionservices, the head-end 16 preferably includes a satellite dish antenna13 and/or a radio frequency (RF) antenna 15 for receiving incomingprogramming. The head-end 16 may also include equipment to playvideotapes and/or to originate live programming that is passed on tosubscribers. Most signals are sent downstream to the subscriber, butsome signals are received upstream such as when a customer requests apay-per-view program. When a cable company provides Internet access tosubscribers, the head-end often includes the computer system anddatabases needed to provide Internet access. A Cable Modem TerminationSystem (CMTS) is typically located at the head end, which sends andreceives digital cable modem signals on a cable network and is necessaryfor providing Internet services to cable subscribers.

[0026] A cable modem termination system (CMTS) is a component thatexchanges digital signals with cable modems on a cable network. When aCMTS receives signals from a cable modem, it converts these signals intoInternet Protocol (IP) packets, which are then sent to an IP router fortransmission across the Internet. When a CMTS sends signals to a cablemodem, it modulates the downstream signals for transmission across thecable to the cable modem. All cable modems can receive from and sendsignals to the CMTS but not to other cable modems on the line.

[0027] In the exemplary communication system 10, the head end 14 passesprogramming and cable modem signals in the downstream direction to oneor more host digital terminals (HDTs) 16 via an optical fiber(s) 18. Thehead end 14 receives cable modem signals and other signals in theupstream direction from the HDT(s) 16 via an optical fiber(s) 20. Inaddition to having a connection to the head end 14 for receivingprogramming and exchanging cable modem signals, the HDT also preferablyincludes a connection to the plain old telephone service (POTS) 17 andoptionally a connection to a data network 19. The HDT 16 is preferablycoupled to a plurality of optical node devices 22 such as opticalnetwork units (ONUs) 22 via optical fibers 24 wherein a single fibercouples a single ONU 22 to a HDT 16. Signals collected by the HDT 16 arecollected and multiplexed onto a single optical fiber to be transmittedto an ONU 22. The HDT 16 also receives optical signals from the ONUs 22,demultiplexes the signals and transmit the signals to their properdestination, i.e., the head end 14, the POTS system 17, or the datanetwork 19.

[0028] Exemplary HFC Network Architecture

[0029] Referring now to FIG. 2, shown in more detail is an exemplaryportion of a HFC network that includes a head end 14 and a network node16. The head end shown is preferably located at a central office (CO)and the network node 16 is preferably a HDT or POP located at a CO. Thehead end 14 preferably includes an electrical signal combining device 40such as an adder, an electrical-to-optical (E/O) converter device 42, anoptical-to-electrical (O/E) converter device 44, a cable modemtransmission system (CMTS) 46, a set top box transmission system (STBTS)48, an XMTS 50, and a communication link 52 for connection to arouter/switch 54 that provides communication paths to a datacommunication network. The head end 14 and the HDT 16 cooperate to sendsignals downstream (DS) from the head end 14 to the ONU 22 (andultimately to a subscriber's home or business location). The head end 14and the HDT 16 also cooperate to send signals (that originate from asubscriber's home or business location) upstream (US) on a return path(RP) from the ONU 22 to the HDT 16 and finally to the head end.

[0030] In the DS path in the head end 14, the electricalsignal-combining device 40 receives electrical signals that are to betransmitted to subscribers and combines them in the frequency domain.Preferably the electrical signal combining device 40 receives broadcastcable signal transmissions (BCST) and narrow-cast cable signaltransmissions (NCST), such as pay-per-view stations, combines thesecable signals with cable modem transmission signals from the CMTS 46,and forwards the combined signals to the E/O converter device 42. TheE/O converter device 42 preferably includes a laser diode 43 that isused to convert the combined electrical signals to a light wave signalat a wavelength λ₁ that can be transported downstream over the opticalfiber 18 to the HDT 16. In the embodiment shown in FIG. 2, the signalsare transmitted over the optical fiber 18 at a wavelength λ₁ in the 1310nm (nano-meters) window.

[0031] In the US path in the head end 14, the O/E converter device 44receives signals at a wavelength λ₅ from the HDT 16 via the opticalfiber 20. In the embodiment shown in FIG. 2, the RP signals aretransmitted over the optical fiber 20 at a wavelength λ₅ in the 1310 nmwindow. The RP signals preferably include set top box (STB) signals, XMsignals, and cable modem (CM) signals. The O/E converter device 44,which preferably includes a photo diode 45, converts the light wavesignal at the wavelength λ₅ to electrical signals. The convertedelectrical signals are forwarded to the appropriate termination system,the CMTS 46, the STBTS 48, or the XMTS 50. The termination systems 51preferably have a high bandwidth link 52 to a Router/Switch 54 forexchanging data with a public network such as an IP network. The highbandwidth link 52 in the example of FIG. 2 is a 100 Bt Ethernet link,however, other communication links could be used such as a GigabitEthernet link and others. The termination systems 51 also preferablyhave a communication path 55 to the electrical signal-combining device40 for sending signals downstream over the DS path.

[0032] In the DS path in the HDT 16, a signal modification device 60 ispreferably provided that comprises an O/E converter 62 and an E/Oconverter 64. The O/E converter 62 preferably includes a photo diode 63for converting optical signals received from the head end 16 via theoptical fiber 18 to electrical signals. The E/O converter 64 preferablyincludes a laser diode 65 for converting electrical signals to opticalsignals at a wavelength λ₂ where the wavelength λ₂ may or may not beequal to the wavelength λ₁. In the embodiment shown, the wavelength λ₂is preferably in the 1550 nm window. The signal modification device 60is not required for the DS path in this embodiment but is preferablyused to allow for local signals to be inserted into the DS path to anONU. After producing optical signals at the wavelength λ₂, the opticalsignals are forwarded to a fiber optic amplifier/splitter stage 66 thatpreferably includes a fiber optical amplifier (FOA) 68 and a splitter70. The fiber optic amplifier/splitter stage 66 amplifies the opticalsignals at wavelength λ₂, splits the amplified optical signals into aplurality of split optical signals and forwards each split opticalsignal to a separate splitter wavelength division multiplexercross-connect (SWX) 72. In the embodiment shown the splitter 70 is a 1:4splitter, however, other splitters, such as a 1:8 splitter, could beused.

[0033] Shown in FIG. 2 is one such SWX 72, however, a plurality of SWXspreferably is provided. The SWX 72 preferably includes a splitter 74that has a plurality of outputs (32 are shown in this embodiment). Eachoutput of the splitter 74 is paired with a wavelength divisionmultiplexer (WDM) stage 76. Shown in FIG. 2 is one such output/WDM pair,however, a plurality of output/WDM pairs is preferably provided. The WDMstage 76 combines the optical signals at wavelength λ₂ that are receivedfrom the splitter 74 with optical signals at wavelength λ₃ that aregenerated by one of the optical interface units (OIUs) 78 and forwardsthe combined multi-wavelength signals to an ONU 22 via an optical fiber24. The OIUs 78 preferably have a public network communication path 79to a public network via, for example, a digital loop carrier (DLC) 80and an ATM network 82 for providing POTS (plain old telephone services)and/or data, such as DSL services, to subscribers. Consequently the OIUs78, via an optical signal on a single fiber 77, can forward POTS anddata signals from the public network to subscribers from the group offibers 81. In the embodiment shown, the wavelength λ₃ is preferably inthe 1310 nm window. Each WDM stage 76 preferably exchanges signals witha single OIU 78 via an optical fiber 77 and exchanges signals with asingle ONU 22 via an optical fiber 24. Consequently, preferably there isa single WDM stage 76 corresponding to each OIU 78, and each WDM/OIUpair can exchange signals with a single ONU 22.

[0034] In the US path from the ONU 22, optical signals at a wavelengthλ₄ are transmitted from the ONU 22 to the associated OIU 78 via a singleoptical fiber 24 and a single optical fiber 77. Each ONU 22 communicateswith a single OIU 78. In the embodiment shown, the wavelength λ₄ isapproximately equal to the wavelength λ₃, which is preferably in the1310 nm window. The light signals in the 1310 nm window are able totravel in both directions on the single fiber optic cable 24 and singlefiber optic cable 77. Each OIU 78 receives optical signals, converts theoptical signals to electrical signals, and forwards the electricalsignals to the appropriate destination. For example, POTS signals aretransmitted to the public network via the public network communicationpath 79, the DLC 80, and the ATM network 82. STB, XM, and CM signals areforwarded by the OIUs via a plurality of copper wires 83 to the returnpath combiner cross-connect (RCX) 84. There is a separate copper wire 83for each OIU 78 that electrically couples that OIU 78 to the RCX 84. TheRCX 84 multiplexes the signals coming over the plurality of copper wires78 onto a single line 85. The RCX 84 combines multiple signals frommultiple OIUs 78 into one signal on one cable 85. The multiplexedsignals are provided to a return path (RP) transmitter 86 that includesa laser diode 87 for converter the RP electrical signals to RP opticalsignals for transmission over optical fiber 20 to the head end 14. Inthe embodiment shown, the RP optical signals are at a wavelength λ₅wherein the wavelength λ₅ is preferably in the 1310 nm window.

[0035] Exemplary OIU Embodiments for Providing POTS at HDT/POP

[0036] Referring now to FIGS. 3A and 3B, illustrated are exemplaryportions of optical interface units (OIUs) associated with exemplarydigital terminal equipment (FIG. 3A) and optical node devices (FIG. 3B).With reference to FIG. 3A, optical signals at the wavelength λ₂, whichin this example is in the 1550 nm window, are passed to a fiber opticamplifier/splitter stage 66, wherein in this example the FOA is anerbium doped fiber amplifier (EDFA). The fiber optic amplifier/splitterstage 66 amplifies the optical signals at wavelength λ₂, splits theamplified optical signals into a plurality of split optical signals andforwards each split optical signal to a separate splitter wavelengthdivision multiplexer cross-connect stage (SWX) 72. The SWX 72 preferablyincludes a splitter 74 and a plurality of wavelength divisionmultiplexer (WDM) stages 76. The WDM stage 76 combines the opticalsignals at wavelength λ₂ with optical signals at wavelength λ₃ (which inthis example is in the 1310 nm window) that are generated by one of theoptical interface units (OIUs) 78 and forwards the combinedmulti-wavelength signals to an ONU 22 via an optical fiber 24.

[0037] As illustrated, the OIU 78 comprises an optical coupler 92, adiplexer 94, an O/E converter 96 that includes a photo diode (PD), andan E/O converter 98 that includes a laser diode (LD). DS signals such asPOTS signals are provided to the E/O converter 98 where they areconverted to optical signals at wavelength λ₃. The optical signals arethen passed in turn to the diplexer 94, the optical coupler 92, and theWDM stage 76 for transmission to an ONU 22. As illustrated in FIG. 3C,the signals modulated as optical signals at wavelengths λ₂ and λ₃preferably include POTS at 0-7.5 MHz in the electrical domain, highbandwidth data at 90-110 MHz, and subcarrier modulation (SCM) data suchas narrow-cast programming at 550-870 MHz.

[0038] In the upstream direction, optical signals at wavelength λ₄ thatare received from an ONU 22 are passed in turn to the WDM stage 76, theoptical coupler 92, the diplexer 94, and the O/E converter 96. The O/Econverter 96 converts the optical signals to electrical signals wherethey can be further processed. As illustrated in FIG. 3C, the signalsthat could be modulated as an optical signal at wavelength λ₄ includePOTS at 0-7.5 MHz in the electrical domain, high bandwidth data at 70-90MHz, RF return from a cable modem or set top box at 9-65 MHz, andNarrow-cast data at 500-870 Mhz.

[0039] With reference to FIG. 3B, the ONU also comprises an OIU. Anexemplary OIU 100 in the ONU comprises an optical coupler 102, adiplexer 104, a first O/E converter 106, a second O/E converter 108, andan E/O converter 110. In the downstream direction from the HDT, the OIU100 receives signals at different wavelengths λ₂ and λ₃. In thisexample, optical signals in the 1550 nm window are received at theoptical coupler 102, forwarded to the triplexer 104, and routed to thefirst O/E converter 106 where the signals are converted to electricalsignals and forwarded for further processing. Optical signals in the1310 nm window are received at the optical coupler 102, forwarded to thediplexer 104, and routed to the second O/E converter 108 where thesignals are converted to electrical signals and forwarded for furtherprocessing. In the upstream direction, electrical signals are receivedby the E/O converter 110 where they are converted to optical signals atwavelength λ₄. The optical signals are then passed in turn to thetriplexer 104 and the optical coupler 102 for transmission upstream tothe HDT.

[0040] Referring now to FIG. 4, a controller circuit 112 is provided inthe HDT OIU 78 for interfacing with a POTS source and for providing POTSsignals from the POTS source to a laser driver 114. The signal outputfrom the laser driver 114 is fed to the laser diode in the E/O converter98 for conversion to optical signals and for transmission downstream tothe ONU. POTS signals flowing upstream from the ONU are received anddirected to the O/E converter 96, which converts the optical signals toelectrical signals and forwards the signals to the controller circuit112. The controller circuit 112 processes the signals and forwards themto the POTS source. RF signals flowing upstream from the ONU arereceived and directed to the O/E converter 96, which converts theoptical signals to electrical signals and forwards the signals to theRCX 84 for combination with signals from other OIUs 78 for forwarding toa return path (RP) transmitter for transmission over an optical fiber toa head end.

[0041] Referring now to FIG. 5, a controller circuit 116 is provided inthe ONU OIU 100 for interfacing with a POTS line and for providing POTSsignals from the POTS line to a laser driver 114. The signal output fromthe laser driver 118 is fed to the laser diode in the E/O converter 110for conversion to optical signals and for transmission downstream to theHDT. POTS signals flowing downstream in the 1310 nm window from the HDTare received and directed to the second O/E converter 108, whichconverts the optical signals to electrical signals and forwards thesignals to a receiver 120 and then to the controller circuit 116. Thecontroller circuit 116 processes the signals and forwards them to thePOTS line. RF signals flowing downstream with the optical signals in the1550 nm window from the HDT are received and directed to the first O/Econverter 106, which converts the optical signals to electrical signalsand forwards the signals to the diplexer 122 for forwarding by cable toa splitter 124 and/or subscribers. RF signals flowing upstream fromsubscribers are received and directed to the diplexer 122 and thenforwarded to the laser driver 118. The signal output from the laserdriver 118 is fed to the laser diode in the E/O converter 110 forconversion to optical signals and for transmission downstream with theoptical signals in the 1310 nm window to the HDT.

[0042] Alternative Embodiment for Providing POTS and High Speed Data atHDT/POP

[0043] Referring now to FIG. 6, to provide the communication networkwith high speed data services, a modem 126 is provided in the HDT OIU 78for interfacing with a link 128 to a high speed data network (forexample, via an ATM network connection 82). The modem 126 directs highspeed data from the link 128 to the laser driver 114. The signal outputfrom the laser driver 114 is fed to the laser diode in the E/O converter98 for conversion to optical signals and for transmission downstream tothe ONU with the optical signals in the 1310 nm window. High Speed dataflowing upstream from the ONU with the optical signals in the 1310 nmwindow are received and directed to the O/E converter 96, which convertsthe optical signals to electrical signals and forwards the signals tothe modem 126. The modem 126 then transmits the high speed data via thelink 128 to the high speed data network. POTS data and cable programmingdata are handled in the HDT in a manner similar to that described withreference to FIG. 4.

[0044] Referring now to FIG. 7, to provide the ONU with high speed dataservices, a modem 130 is provided in the ONU OIU 100 for linking withsubscribers to provide the high speed data services to the subscribers.High speed data received from the downstream optical signals in the 1310nm window are directed to the second O/E converter 108, which convertsthe optical signals to electrical signals and forwards the signals tothe modem 130. The modem 130 processes the signals and forwards them tosubscribers. High speed data signals flowing upstream from subscribersare received by the modem 130 and directed to the laser driver 118.

[0045] The signal output from the laser driver 118 is fed to the laserdiode in the E/O converter 110 for conversion to optical signals and fortransmission downstream with the optical signals in the 1310 nm windowto the HDT. POTS data and cable programming data are handled in the HDTin a manner similar to that described with reference to FIG. 4.

[0046] Alternative Embodiment for Providing High Speed Data and VOD atHDT/POP

[0047] Referring now to FIG. 8, to provide the communication networkwith video on demand (VOD) services in addition to high speed dataservices, a multi-diplexer 132 is provided in the HDT OIU 78. The modem126 directs high speed data from the link 128 to the multi-diplexer 132.The multi-diplexer 132, in turn, sends the high speed data from the link128 to the laser driver 114. The signal output from the laser driver 114is fed to the laser diode in the E/O converter 98 for conversion tooptical signals and for transmission downstream to the ONU the opticalsignals in the 1310 nm window. High Speed data flowing upstream from theONU the optical signals in the 1310 nm window are received and directedto the O/E converter 96, which converts the optical signals toelectrical signals and forwards the signals to the multi-diplexer 132.The multi-diplexer 132, in turn, sends the high speed data to the modem126. The modem 126 then transmits the high speed data via the link 128to the high speed data network. POTS data is handled in the HDT in amanner similar to that described with reference to FIG. 4.

[0048] RF signals flowing upstream from the ONU as a part of the opticalsignals in the 1310 nm window are received and directed to the O/Econverter 96, which converts the optical signals to electrical signalsand forwards the signals to the multi-diplexer 132. The multi-diplexer132, in turn, sends the high speed data to the RCX 84 for combinationwith signals from other OIUs 78 for forwarding to a CMTS/VODDistribution system 134. RF signals flowing downstream from the CMTS/VODDistribution system 134, such as signals containing video on demandsignals, are routed from the CMTS/VOD Distribution system 134 to the RCX84 and then to the multi-diplexer 132. The multi-diplexer 132, in turn,sends the VOD signals to the laser driver 114. The signal output fromthe laser driver 114 is fed to the laser diode in the E/O converter 98for conversion to optical signals and for transmission downstream to theONU the optical signals in the 1310 nm window.

[0049] Referring now to FIG. 9, to provide the ONU with video on demand(VOD) services in addition to high speed data services, adiplexer/combiner 136 is provided in the ONU OIU 100. High speed datareceived from the downstream optical signals in the 1310 nm window aredirected to the second O/E converter 108, which converts the opticalsignals to electrical signals and forwards the signals to thediplexer/combiner 136. The diplexer/combiner 136 passes the signals tothe modem 130. The modem 130, in turn, forwards the signals tosubscribers. High speed data signals flowing upstream from subscribersare received by the modem 130 and directed to the diplexer/combiner 136.The diplexer/combiner 136 forwards the high speed data to the laserdriver 118. The signal output from the laser driver 118 is fed to thelaser diode in the E/O converter 110 for conversion to optical signalsand for transmission downstream the optical signals in the 1310 nmwindow to the HDT. POTS data is handled in the HDT in a manner similarto that described with reference to FIG. 4.

[0050] RF signals flowing downstream the optical signals in the 1550 nmwindow from the HDT, such as cable programming signals, are received anddirected to the first O/E converter 106, which converts the opticalsignals to electrical signals and forwards the signals to thediplexer/combiner 1362. RF signals flowing downstream the opticalsignals in the 1310 nm window from the HDT, such as VOD signals, arereceived and directed to the second O/E converter 108, which convertsthe optical signals to electrical signals and forwards the signals tothe diplexer/combiner 136. The diplexer/combiner 136 combines the VODsignals and the cable programming signals in the electrical domain andforwards the combined signals by cable to a splitter 124 and/orsubscribers. RF signals flowing upstream from subscribers are receivedand directed to the diplexer/combiner 136 and then forwarded to thelaser driver 118. The signal output from the laser driver 118 is fed tothe laser diode in the E/O converter 110 for conversion to opticalsignals and for transmission downstream the optical signals in the 1310nm window to the HDT.

[0051] Referring now to FIG. 10, to provide the ONU with video on demand(VOD) services in addition to high speed data services, but without POTS(such as for use with a cable TV company that does not providetelephonic services), a diplexer/combiner 142 is provided in the ONU OIU100. High speed data received from the downstream optical signals in the1550 nm window are directed to the O/E converter 108, which converts theoptical signals to electrical signals and forwards the signals to thediplexer/combiner 142. The diplexer/combiner 142 passes the signals tothe subscribers via cable and the RF splitter 124 to a cable modemassociated with the subscriber. High speed data signals flowing upstreamfrom subscribers are received by the diplexer/combiner 136 and forwardedby the diplexer/combiner 136 to the laser driver 118. The signal outputfrom the laser driver 118 is fed to the laser diode in the E/O converter110 for conversion to optical signals and for transmission downstreamthe optical signals in the 1310 nm window to the HDT.

[0052] RF signals flowing downstream the optical signals in the 1550 nmwindow from the HDT, such as cable programming signals, are received anddirected to the first O/E converter 106, which converts the opticalsignals to electrical signals and forwards the signals to thediplexer/combiner 136. RF signals flowing upstream from subscribers arereceived and directed to the diplexer/combiner 136 and then forwarded tothe laser driver 118. The signal output from the laser driver 118 is fedto the laser diode in the E/O converter 110 for conversion to opticalsignals and for transmission downstream the optical signals in the 1310nm window to the HDT. A pilot tone and processor 138 is also provided toprovide calibration signals to the laser driver 118.

[0053] Conclusion

[0054] Other variations from these systems and methods should becomeapparent to one of ordinary skill in the art without departing from thescope of the invention defined by the claims. The preferred embodimentshave been described with reference to FTTC HFC systems but the inventiondescribed by the claims could be applicable to other network systems.

[0055] The embodiments described herein and shown in the drawings areexamples of structures, systems or methods having elements correspondingto the elements of the invention recited in the claims. This writtendescription and drawings may enable those skilled in the art to make anduse embodiments having alternative elements that likewise correspond tothe elements of the invention recited in the claims. The intended scopeof the invention thus includes other structures, systems or methods thatdo not differ from the literal language of the claims, and furtherincludes other structures, systems or methods with insubstantialdifferences from the literal language of the claims. It is also to beunderstood that the invention is not limited to use with FTTC systemsunless explicitly limited by the claims.

The following is claimed:
 1. A communication system for providing highspeed data services to a subscriber using optical fibers, thecommunication system comprising: a first optical interface unit (OIU) ina network node element, the first OIU comprising a firstelectrical-to-optical (E/O) circuit, a first optical-to-electrical (O/E)circuit, a first diplexer device, and a first modem, the first E/Ocircuit being operative to receive first electrical signals, convert thefirst electrical signals to first optical signals of a first wavelength,and transmit downstream on an optical fiber the first optical signals,the first O/E circuit being operative to receive second optical signalsfrom the optical fiber, convert the second optical signals to secondelectrical signals, and to transmit the second electrical signalsupstream, the first diplexer device being coupled between the opticalfiber and the first E/O circuit and being coupled between the opticalfiber and the first O/E circuit, the first modem being coupled betweenthe first O/E circuit and a high speed data source and between the firstE/O circuit and the high speed data source for providing a high speeddata path in the OIU; a second optical interface unit (OIU) in anoptical node device, the second OIU comprising a second E/O circuit, asecond O/E circuit, a third O/E circuit, a first triplexer device, and asecond modem, the second E/O circuit being operative to receive thirdelectrical signals, convert the third electrical signals to the secondoptical signals of a second wavelength, and transmit upstream on theoptical fiber the second optical signals, the second O/E circuit beingoperative to receive third optical signals of a third wavelength fromthe optical fiber, convert the third optical signals to fourthelectrical signals, and to transmit the fourth electrical signalsdownstream to a subscriber, the third O/E circuit being operative toreceive the first optical signals from the optical fiber, convert thefirst optical signals to fifth electrical signals, and to transmit thefifth electrical signals downstream to a subscriber, the first triplexerdevice being coupled between the optical fiber and the second E/Ocircuit, the first triplexer device being coupled between the opticalfiber and the second O/E circuit, and the first triplexer device alsobeing coupled between the optical fiber and the third O/E circuit, thesecond modem being coupled between the third O/E circuit and a highspeed data subscriber and between the second E/O circuit and the highspeed data subscriber for providing a high speed data path in the secondOIU; and the optical fiber being used for transporting the first,second, and third optical signals between the network node element andthe optical node device.
 2. The system of claim 1 wherein the opticalnode device comprises an optical network unit (ONU)
 3. The system ofclaim 1 wherein the communication system comprises a fiber-to-the-curb(FTTC) system.
 4. The system of claim 1 wherein the first electricalsignals comprise downstream high bandwidth data.
 5. The system of claim4 wherein the second electrical signals comprise upstream high bandwidthdata.
 6. The system of claim 1 wherein the first electrical signalscomprise downstream subcarrier modulated data.
 7. The system of claim 6wherein the second electrical signals comprise upstream subcarriermodulated data.
 8. The system of claim 1 wherein the first electricalsignals comprise downstream POTS signals, downstream high bandwidthdata, and downstream subcarrier modulated data.
 9. The system of claim 8wherein the downstream POTS signals are in a frequency range of about0-7.5 MHz, the downstream high bandwidth data is in a frequency range ofabout 90-110 MHz, and the downstream subcarrier modulated data is in afrequency range of about 500-870 Mhz.
 10. The system of claim 8 whereinthe second electrical signals comprise upstream POTS signals, upstreamhigh bandwidth data, upstream RF return data, and upstream subcarriermodulated data.
 11. The system of claim 10 wherein the upstream POTSsignals are in a frequency range of about 0-7.5 MHz, the upstream highbandwidth data is in a frequency range of about 70-90 MHz, the upstreamRF return data is in a frequency range of about 9-65 MHz, and thedownstream subcarrier modulated data is in a frequency range of about500-870 Mhz.
 12. The system of claim 1 wherein the network nodecomprises a point-of-presence (POP) in a central office (CO).
 13. Thesystem of claim 1 wherein the network node comprises a host digitalterminal (HDT).
 14. The system of claim 13 wherein the HDT is located ata central office (CO).
 15. The system of claim 1 wherein the firstwavelength is in the 1310 nano-meter (nm) window, the second wavelengthis in the 1310 nm window, and the third wavelength is in the 1550 nmwindow.
 16. The system of claim 1 wherein the first wavelength is in the1550 nm window, the second wavelength is in the 1550 nm window, and thethird wavelength is in the 1550 run window.
 17. The system of claim 1wherein the first wavelength is in the 1310 nano-meter (nm) window, thesecond wavelength is in the 1310 nm window, and the third wavelength isin the 1310 nm window.
 18. The system of claim 1 wherein the firstwavelength is in the 1550 nm window, and the second wavelength is in the1550 nm window, and the third wavelength is in the 1310 nm window. 19.The system of claim 1 further comprising a multi-diplexer in the firstOIU, the multi-diplexer being coupled between the modem, a return pathcombiner cross-connect (RCX), the first O/E circuit, and the first E/Ocircuit.
 20. The system of claim 19 further comprising adiplexer/combiner in the second OIU, the diplexer/combiner being coupledbetween the second O/E circuit, the third O/E circuit, the second E/Ocircuit, the second modem, and an RF path to a subscriber.